Integrally Blow-Moulded Bag-in-Container Comprising an Inner Layer and an Outer Layer Comprising Energy Absorbing Additives, Preform for Making It and Process for Producing it

ABSTRACT

A preform for an integrally blow-moulded bag-in-container uses an inner layer and an outer layer, wherein the preform forms a two-layer container upon blow-moulding, and wherein the obtained inner layer of the container releases from the thus obtained outer layer upon introduction of a gas at a point of interface between the two layers. At least one of the inner and outer layers includes at least one additive allowing both inner and outer layers to reach their respective blow-moulding temperatures substantially simultaneously.

FIELD OF THE INVENTION

The present invention relates in general to new developments indispensing bag-in-containers and, in particular, to integrallyblow-moulded bag-in-containers made of different materials. It alsorelates to a method for producing the bag-in-containers and, inparticular, to preforms used for their production, as well as a methodfor producing said preform.

BACKGROUND OF THE INVENTION

Bag-in-containers, also referred to as bag-in-bottles or bag-in-boxesdepending on the geometry of the outer vessel, all terms consideredherein as being comprised within the meaning of the termbag-in-container, are a family of liquid dispensing packaging consistingof an outer container comprising an opening to the atmosphere—themouth—and which contains a collapsible inner bag joined to saidcontainer and opening to the atmosphere at the region of said mouth. Thesystem must comprise at least one vent fluidly connecting the atmosphereto the region between the inner bag and the outer container in order tocontrol the pressure in said region to squeeze the inner bag and thusdispense the liquid contained therein.

Traditionally, bag-in-containers were—and still are—produced byindependently producing an inner bag provided with a specific neckclosure assembly and a structural container (usually in the form of abottle). The bag is inserted into the fully formed bottle opening andfixed thereto by means of the neck closure assembly, which comprises oneopening to the interior of the bag and vents fluidly connecting thespace between bag and bottle to the atmosphere. Examples of suchconstructions can be found inter alia in U.S. Pat. Nos. 3,484,011,3,450,254, 4,330,066, and 4,892,230. These types of bag-in-containershave the advantage of being reusable, but they are very expensive andlabour-intensive to produce.

More recent developments focused on the production of “integrallyblow-moulded bag-in-containers” thus avoiding the labour intensive stepof assembling the bag into the container, by blow-moulding a polymericmultilayer preform into a container comprising an inner layer and anouter layer, such that the adhesion between the inner and the outerlayers of the thus produced container is sufficiently weak to readilydelaminate upon introduction of a gas at the interface. The “innerlayer” and “outer layer” may each consist of a single layer or aplurality of layers, but can in any case readily be identified, at leastupon delamination. Said technology involves many challenges and manyalternative solutions were proposed.

The multilayer preform may be extruded or injection moulded (cf. U.S.Pat. No. 6,238,201, JPA10128833, JPA11010719, JPA9208688, U.S. Pat. No.6,649,121. When the former method is advantageous in terms ofproductivity, the latter is preferable when wall thickness accuracy isrequired, typically in containers for dispensing beverage.

The formation of the vents fluidly connecting the space or interfacebetween bag and bottle to the atmosphere remains a critical step inintegrally blow-moulded bag-in-containers and several solutions wereproposed in e.g., U.S. Pat. Nos. 5,301,838, 5,407,629, JPA5213373,JPA8001761, EPA1356915, U.S. Pat. No. 6,649,121, JPA10180853.

One redundant problem with integrally blow-moulded bag-in-containers isthe choice of materials for the inner and outer layers which must beselected according to strict criteria of compatibility in terms ofprocessing on the one hand and, on the other hand, of incompatibility interms of adhesion. These criteria are sometimes difficult to fulfil incombination as illustrated below. This problem does not arise in thefield of blow-moulding co-layer plastic containers, wherein the adhesionbetween layers is maximized in order to avoid delamination, because bestadhesion is obtained with similar materials, which generally havesimilar thermal properties. Consequently, finding materials beingcompatible in terms of both processing and adhesion as for thefabrication of co-layer containers is generally less problematic thanfinding materials being compatible in terms of processing andincompatible in terms of adhesion as for the fabrication ofbag-in-containers.

Addressing processing compatibility, EPA1356915 and U.S. Pat. No.6,649,121 proposed that the melting temperature of the outer layershould be higher than the one of the inner layer in order to allowproduction of integral preforms by injection moulding the outer layerfirst, followed by injecting thereover the inner layer. Examples ofmaterials for the outer layer given by the authors include PET and EVOH,whilst polyethylene is given as an example for the inner layer. Thoughthis materials selection could result advantageous for the injectionmoulding production of the preforms, it is far from optimal for theblow-moulding step since polyethylene and PET are characterized by quitedifferent blow-moulding temperatures. Again, in U.S. Pat. No. 6,238,201a method is described including co-extruding a two layer parisonfollowed by blow-moulding said parison into a bag-in-container whereinthe outer layer preferably comprises an olefin and the inner layer anamorphous polyamide.

Concerning the materials choice for a weak interfacial adhesion requiredfor ensuring proper delamination of the inner layer from the outer layerupon use, mention is made in JPA2005047172 of “mutually non-adhesivesynthetic resins.” In the review of the background art in U.S. Pat. No.5,921,416 the use of release layers interleafed between inner and outerlayers, forming three- or five-layer structures is mentioned. An exampleof such construction is described in U.S. Pat. No. 5,301,838 whichdiscloses a complex five layer preform comprising three PET layersinterleafed by two thin layers of a material selected from the group ofEVOH, PP, PE, PA6. Here again, beside the complexity involved with theproduction of such preforms, substantial differences in blow-mouldingtemperatures characterize these different materials.

Alternatively and surprisingly it has been discovered that excellentdelamination results between the inner and outer layers can be obtainedalso with preforms wherein both inner and outer layers consist of thesame material. Similar results were obtained both with preformassemblies as well as with integral preforms. In the case of integral,over-moulded preforms, it is generally believed that better results areobtained with semi-crystalline polymers.

The same polymer is considered in contact on either side of theinterface between the inner and outer layers in the following cases:

-   -   inner and outer layers consist of the same material (e.g.,        PET_(inner)-PET_(outer), regardless of the specific grade of        each PET); or    -   the inner and outer layers consist of a blend or copolymer        having at least one polymer in common, provided said polymer in        common is at the interface, whilst the differing polymer is        substantially absent of said interface (e.g., (0.85 PET+0.15        PA6)_(inner)(0.8 PET+0.2 PE)_(outer).        The presence in a layer of low amounts of additives is not        regarded as rendering the material different, so far as they do        not alter the interface substantially.

Although in case the same material is used for the inner and outerlayers, there is no difference in blow-moulding temperature betweenlayers, the heating rate of the two layers can be substantiallydifferent due to the wide difference in thicknesses between the innerand outer layers. Moreover, the inner layer is sheltered by the thick,outer layer from the IR-radiation of the IR-oven usually used to bringthe preform to blow-moulding temperature. It follows that even formaterials having little or no difference in blow-moulding temperature,there can be a problem to heat up simultaneously both layers to theirprocess temperatures.

In order to overcome the problem of different blow-moulding temperaturesor heating rates of the materials forming the inner and outer layers ofblow-moulded multilayer containers, the different preform components maybe heated separately in different ovens to heat them at their respectiveblow-moulding temperature (cf. e.g., JPA57174221). This solution,however, is expensive in terms of equipment and space and does not applyto integral preforms, which inner and outer layers cannot be separated.

The use of energy absorbing additives in preforms for blow-mouldingmonolayer containers has been proposed for shortening the heating stageand thus saving energy in, e.g., U.S. Pat. Nos. 5,925,710, 6,503,586,6,034,167, 4,250,078, 6,197,851, 4,476,272, 5,529,744, and the likes.The use of energy absorbing additives has also been proposed in theinner layer of blow-moulded co-layer containers (i.e., not meant todelaminate) to compensate for the greater strain undergone by the innerlayer compared with the outer layer during blow-moulding operation. Inco-layer containers it is very important that the inner layer is allowedto stretch sufficiently to contact and adhere to the outer layer oversubstantially the whole of their interface. The inner layer containingthe energy absorbing additives is thus heated to a higher temperaturethan the outer layer and can be stretched further to adhere to the outerlayer.

The above considerations do not apply in the field of bag-in-containers,since a good adhesion between the inner and outer layers is exactly whatis to be avoided. Furthermore, preforms for the production of integrallyblow-moulded bag-in-containers clearly differ from preforms for theproduction of blow-moulded co-layered containers, wherein the variouslayers of the container are not meant to delaminate, in the thickness ofthe layers. A bag-in-container is comprised of an outer structuralenvelope containing a flexible, collapsible bag. It follows that theouter layer of the container is substantially thicker than the innerbag. This same relationship can of course be found in the preforms aswell, which are characterized by an outer layer being substantiallythicker than the inner layer. This has a detrimental effect on theheating efficacy of IR-lamps on heating the inner layer, since thelatter is separated from the IR-lamps by the thick wall of the outerlayer.

It follows from the foregoing that there remains a need in the art forsolutions for compensating the difference in blow-moulding temperaturesand heating rates between the “mutually non-adhesive synthetic resins”(cf. JP2005047172) of the inner and outer layers of a preform for theproduction of integrally blow-moulded bag-in-containers.

SUMMARY OF THE INVENTION

The present invention is defined in the appended independent claims.Preferred embodiments are defined in the dependent claims. In particularthe present invention relates to a preform for blow-moulding abag-in-container. An inner layer and an outer layer are used, whereinsaid preform forms a two layer container upon blow-moulding, and whereinthe obtained inner layer of the container releases from the thusobtained outer layer upon introduction of a gas at a point of interfacebetween said two layers. At least one of the inner and outer layersincludes at least one additive allowing both inner and outer layers toreach their respective blow-moulding temperatures substantiallysimultaneously when heated together in a single oven.

It also concerns a process for producing a bag-in-container from theabove preform and a bag-in-container thus obtained. Finally the presentinvention relates to the use of energy absorbing additives for thesubstantially simultaneous heating to the respective blow-mouldingtemperatures of the inner and outer layers of a preform forblow-moulding a bag-in-container.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross-sectional representation of a firstembodiment of a preform according to the present invention and thebag-in-container obtained after blow-moulding thereof.

FIG. 1B is a schematic cross-sectional representation of a secondembodiment of a preform according to the present invention and thebag-in-container obtained after blow-moulding thereof.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to appended FIGS. 1A and 1B, there is illustrated anintegrally blow-moulded bag-in-container (2) and a preform (1)&(1′) forits manufacturing. The preform (1) comprises an inner layer (11) and anouter layer (12) joined at least at the level of the neck region (6) byan interface (shown on the right hand side). The region between innerand outer layers (11) and (12) may either consist of an interface (14)wherein the two layers are substantially contacting each other, orcomprise a gap (14′) in fluid communication with at least one vent (3)opening to the atmosphere in (4).

Many vent geometries have been disclosed, and it is not critical whichgeometry is selected. It is preferred, however, that the vent be locatedadjacent to, and oriented coaxially with said preform's mouth (5) asillustrated in FIG. 1. More preferably, the vents have the shape of awedge with the broad side at the level of the opening (4) thereof andgetting thinner as it penetrates deeper into the vessel, until the twolayers meet to form an interface (14) at least at the level of the neckregion. This geometry allows for a more efficient and reproducibledelamination of the inner bag upon use of the bag-in-container. Thecontainer may comprise one or several vents evenly distributed aroundthe lip of the bag-in-container's mouth. Several vents are advantageousas they permit the interface of the inner and outer layers (21) and (22)of the bag-in-container (2) to release more evenly upon blowingpressurized gas through said vents. Preferably, the preform comprisestwo vents opening at the vessel's mouth lip at diametrically opposedpositions. More preferably, three, and most preferably, at least fourvents open at regular intervals of the mouth lip.

The preform may consists of an assembly of two separate preforms (11)and (12) produced independently from one another and thereafterassembled such that the inner preform (11) fits into the outer preform(12). This solution allows for greater freedom in the design of the neckand vents. Alternatively, it can be an integral preform obtained byinjection moulding one layer on top of the other. The latter embodimentis advantageous over the assembled preform in that it comprises noassembly step and one production station only is required for thepreform fabrication. On the other hand, the design of the vents inparticular is restricted by this process.

A preform for the production of a typical 8 liter bag-in-container fordispensing beer has an outer layer (12) about 210 mm thick, preferably36 mm, most preferably 45 mm thick, whilst the inner layer generally isabout 0.33 mm thick, preferably 0.31.5 mm, most preferably 0.51 mm thick

Preferred materials for the inner and outer layers of the preform andbag-in-container of the present invention are pairs of differentmaterials selected from the group of polyesters like PET, PEN, PTT, PTN;polyamides like PA6, PA66, PA11, PA12; polyolefins like PE, PP; EVOH;biodegradable polymers like polyglycol acetate (PGAc), polylactic acid(PLA); and copolymers and blends thereof. Materials like PET or PENshould optimally be heated before blow-moulding, whilst polyolefins andpolyamides should be heated. In order to allow for the substantiallysimultaneous heating to the respective process temperatures of theresins of the inner and outer layers of the preform using a single oven,energy absorbing additives are added to the resin having highest processtemperature. It is, however, also possible that both layers compriseenergy absorbing additives of different nature and/or in differentamounts, as long as the time required to arrive at the respectiveprocess temperatures of the materials of the inner and outer layers issubstantially the same.

The additives useful in the present invention The additives that can beused in the present invention may be any compound that selectivelyabsorbs radiation in the wavelength region of 500 to 2000 nm and whichis preferably sufficiently fine not to be visible to the eye. Theycomprise energy absorbing additives and colorants. Examples of energyabsorbing additives include but are not limited to carbon black,graphite, diamond dust, diazonium salts, sulphonium salts (e.g.,triphenylsulphonium bromide), sulfoxonium salts, odonium salts, etc.

The amount of additive present in a layer depends on the additive itselfand on the resins used for the inner and outer layers. A larger amountmay impair stretchability of the layers.

The two layers (11) and (12) of the preform may be connected by aninterface (14) throughout substantially the whole inner surface of theouter layer. Inversely, they may be separated over a substantial area ofthe preform's body by a gap (14) containing air and which is in fluidcommunication with at least one interface vent (3). The latterembodiment is easier to realize when using a preform assembly designedsuch that the inner preform is firmly fixed to the outer preform at theneck region (6) and a substantial gap (14) may thus be formed betweeninner and outer layers (11) and (12).

The bag-in-container (2) of the present invention can be obtained byproviding a preform as described above, at least one layer of whichcomprising energy absorbing additives; bringing each layer of saidpreform to their respective blow-moulding temperatures; fixing the thusheated preform at the level of the neck region with fixing means in theblow-moulding tool; and blow-moulding the thus heated preform to form abag-in-container, wherein, the type and amount of energy absorbingadditives comprised in at least one of the inner and outer layers ofsaid preform are such that said two layers reach their respectiveblow-moulding temperatures substantially simultaneously.

The inner and outer layers (21) and (22) of the thus obtainedbag-in-container are connected to one another by an interface (24) oversubstantially the whole of the inner surface of the outer layer. Saidinterface (24) is in fluid communication with the atmosphere through thevents (3), which maintained their original geometry through theblow-moulding process since the neck region of the preform where thevents are located is held firm by the fixing means and is not stretchedduring blowing.

It is essential that the interface (24) between inner and outer layers(21) and (22) releases upon blowing pressurized gas through the vents ina consistent and reproducible manner. The success of said operationdepends on a number of parameters, in particular, on the interfacialadhesive strength, the number, geometry, and distribution of the vents,and on the pressure of the gas injected. The interfacial strength is ofcourse a key issue and can be modulated by the choice of the materialfor the inner and outer layers, and by the process parameters duringblow-moulding. The pressure-time-temperature window used is of course ofprime importance and greatly depends on the materials selected for theinner and outer layers.

Excellent results can be obtained if the blow-moulding process iscarried out on a preform as described above, of the type wherein a gapcontaining air separates the inner and outer layers over a substantialarea of the preform's body and wherein said gap is in fluidcommunication with at least one interface vent and wherein,

-   -   in a first stage, a gas is blown into the space defined by the        inner layer to stretch the preform, whilst the air in the gap        separating the preform inner and outer layers is prevented from        being evacuated by closing said at least one preform interface        vent with a valve located in the fixing means; and    -   in a second stage, when the air pressure building up in said gap        reaches a preset value, the valve opens thus allowing evacuation        of the air enclosed in the gap.

By this method, the inner layer is prevented from entering into contactwith the outer layer by the air cushion enclosed within the gapseparating the two layers when their respective temperatures are thehighest. As stretching proceeds, the gap becomes thinner and airpressure within the gap increases. When the pressure reaches a presetvalue, the valve closing the vent opening releases, the air is ejected,and the inner layer is permitted to contact the outer layer and form aninterface therewith at a stage where their respective temperatures havedropped to a level where adhesion between the layers cannot build up toany substantial level.

A release agent may be applied at the interface on either or bothsurfaces of the inner and outer layer, which are to form the interfaceof the bag-in-container. In the case the outer layer is injectionmoulded onto the inner layer, the release agent can be applied at theouter surface of the inner layer prior to moulding the outer layer. Anyrelease agents available on the market and best adapted to the materialused for the preform and resisting the blowing temperatures, likesilicon- or PTFE-based release agents (e.g., Freekote) may be used. Therelease agent may be applied just prior to loading the preforms into theblowmoulding unit, or the preforms may be supplied pretreated.

The application of a release agent is particularly beneficial withrespect to the design of the inner layer. Indeed, lowering theinterferential adhesive strength facilitates delamination of the innerlayer from the outer layer and hence reduces stress exerted on the innerlayer upon delamination, as such the inner layer can be designed verythin and flexible without risking that the inner layer is damaged upondelamination. Clearly, the flexibility of the inner bag is a keyparameter for the liquid dispensing and moreover costs savings can beachieved in terms on material savings when the inner layer can bedesigned very thin.

EXPERIMENTAL EXAMPLES

The following examples demonstrate the benefits of the presentinvention. Preforms comprising an inner and outer layers made ofdifferent materials were heated in an oven comprising six IR lamps. Theheating conditions were maintained constant for all the tests. Thetemperatures, T_(inner and) T_(outer), of the inner and outer layerswere measured after residence in the oven and the preforms were thenblow-moulded with a blow pressure of 10 bar in a mould set a temperatureof 83° C. Table 1 below lists the measured temperatures of the inner andouter layers, comments on blow-mouldability, and indicates the values ofthe delamination pressure.

The delamination pressure was determined as follows. The interface ventsof an empty bag-in-container obtained as described above are connectedto a source of pressurized air. Air is injected through the vents at aconstant pressure and the interface between inner and outer layers isobserved; the pressure is increased until delamination pressure isreached. Delamination pressure is defined as the pressure at which theinner bag separates from the outer layer over the whole of theirinterface and collapses. The surfaces of the thus separated layers areexamined for traces of bonding. Preferred results are a low delaminationpressure, of the order of above 0.3 to 0.9 bar overpressure, with notraces of bonding.

1-17. (canceled)
 18. A process for producing a bag-in-containercomprising the following steps: providing a polymer perform having: aninner layer and an outer layer, wherein each of said inner layer andsaid outer layer consists of a single layer comprising PET, said performforms a two layer bag-in-container having a body and neck region uponblow-moulding, said bag-in container comprising a vent connecting theinterface to the atmosphere and wherein the obtained inner layer of saidbag-in-container releases from the obtained outer layer uponintroduction of a pressurized gas at a point of interface between saidtwo layers in the neck region of the bag-in-container; and at least oneof said inner and outer layers includes an additive, the additive isselected from the group consisting of energy absorbing additives andcolorants; heating said perform to blow-moulding temperature in a singleoven; and blow-moulding the heated perform to form the bag-in-container;wherein a type and an amount of the additive in the at least one of theinner and outer layers of said preform are such that said two layersreach their respective blow-moulding temperatures simultaneously. 19.The process according to claim 18, wherein the energy absorbing additiveis selected from the group consisting of; carbon black, graphite,diamond dust, diazonium salts, sulphonium salts, sulfoxonium salts, andiodonium salts.
 20. The process according to claim 18, wherein the innerlayer or the outer layer further comprises at least one selected fromthe group consisting of: polyethylene naphthalate (PEN),polytrimethylene terephthalate (PTT), polyamide (PA), polypropylene(PP), polyethylene (PE), high density polyethylene (HDPE), ethylenevinyl alcohol (EVOH), polyglycolic acid (PGAc), polylactic acid (PLA),and copolymers or blends thereof.
 21. The process according to claim 18,wherein the oven comprises infrared lamps.
 22. The method of claim 18,further comprising filling the inner bag with a liquid.
 23. The methodof claim 22, wherein the liquid is a beverage.
 24. The method of claim22, further comprising releasably attaching a source of pressurized gasto the vent.
 25. The method of claim 24, further comprising injecting apressurized gas from the source of pressurized gas through the vent andinto the interface of the bag-in-container to collapse the inner bag anddispense the liquid contained therein.